A gas turbine engine, such as an aircraft engine, operates in severe environments. Ceramic matrix composite (CMC) components have desirable high temperature mechanical, physical, and chemical properties which allow gas turbine engines to operate at much higher temperatures than current engines with superalloy components. For example, CMC components exhibit a significant amount of damage tolerance when under an applied load when compared to superalloy components. This damage tolerance is due in part to the formation of multiple matrix cracks that aid in the redistribution of stresses.
An issue with CMC components, however, is their lack of environmental durability in combustion environments. For example, the formation of matrix cracks may result in environmental exposure to the fiber and fiber interface coating (typically boron nitride (BN)), which over time, may cause environmental degradation of the CMCs. The environmental degradation of CMCs is temperature and environment dependent. For example, at low temperatures (e.g., below 1000° C.) oxygen may ingress to the fiber unimpeded causing environmental attack at the interface and resulting in embrittlement. At high temperatures (e.g., greater than 1000° C.), silicon dioxide (SiO2) may be formed, which may impede oxygen transport and slow down the degradation of the fiber and the fiber interface. However, the formation of SiO2 may be hindered if water vapor (a combustion reaction product) is present.